We developed the energy harvester employing piezoelectric zinc oxide (ZnO) thin film for application to large vibrational amplitude. To ensure the fracture toughness, stainless steel (SUS304) was employed as a substrate. Also, to prevent the electrical breakdown due to the pinholes in the ZnO film, conformal silicon oxide (SiO₂) layer was inserted between the ZnO film and top electrode. By inserting the SiO₂ layer, power efficiency was much enhanced. As a result, a generated power of 150nW was obtained when acceleration and load resistance were 0.7m/s² and 670kΩ, respectively.